Conformations of some αβ-unsaturated carbonyl compounds. Part I. Infrared spectra of acraldehyde, crotonaldehyde, methyl vinyl ketone, and ethylideneacetone

Abstract

Infrared spectra of acraldehyde, crotonaldehyde, methyl vinyl ketone, and ethylideneacetone in solution and vapour states are reported. Band intensity measurements at temperatures between –110° and 200° are interpreted in terms of conformational equilibrium between the s-trans and non-trans forms of the ketones. The additional enthalpy (ΔH) of the non-trans forms are: [graphic omitted] No evidence is found for more than one form of the aldehydes and the rotational structure of vibrational bands of both acraldehyde and crotonaldehyde suggest these exist in the s-trans conformation. Vibrational assignments are provided for the various conformations detected in these compounds.